1. Field of the Invention
The present invention relates to baseband radar systems, and more particularly, to means for minimizing the susceptibility of such systems to CW and narrow band jamming.
2. Description of the Prior Art
Radar systems utilizing subnanosecond substantially baseband pulses have a wide range of military applications, one of which is as a range sensor in a proximity fuse wherein range resolution and accuracy are of prime importance. These devices, however, though insensitive to multiple target deception and broadband noise jammers because of receiver range gates that are only a few nanoseconds wide, are vulnerable to electronic countermeasures (ECM) such as CW or narrow band jammers operating at frequencies which are of the order of the reciprocal of the substantially baseband pulse. Incident signals of CW jammers in this range present a multiplicity of half cycles within a range gate which appear as baseband pulses to the system's receiver thus providing an opportunity for the jamming signal to exceed the system threshold with each cycle. If a baseband radar system were employed as a terminal altitude sensing device for a free falling bomb, a CW jamming signal could cause the bomb to prematurely explode thus reducing the effectiveness of the weapon. Providing a narrow range gate to reduce the probability of false alarms with each cycle of CW signal concomitantly requires a moving range gate to cover the desired over-all range, thus adding an undesired complexity. To utilize the inherent range resolution and accuracy of baseband radar systems, a means for minimizing its susceptibility to CW, and narrow band jamming is required.